This invention relates to compositions and methods useful for treating plant foliage with an insoluble powdered additive formulation to protect the plant from damage by insects, pests, diseases and browsing animals. More particularly, the invention is useful in binding an insoluble powdered additive formulation to a plant to be protected in such a way that it may be applied during wet or dry weather and is thereafter resistant to washing off in subsequent wet weather.
In the cultivation of plants for food, shelter products, paper or ornamental display it is frequently necessary to protect the plants from disease, insects, and, in some cases, from animal browsing. A common approach is to apply a biologically active formulation to the plant foliage to be protected, which formulation contains a bio-active material that effects a desired result such as, for example, killing an insect infestation. If the purpose of the formulation is long-term effectiveness rather than a quick one-time control, fixing an extended-life active material onto plant foliage becomes a difficult problem with respect to the weather. Rainfall tends to wash the active materials from the foliage and into the soil where it generally has little effect on foliage-attacking pests or disease. Thus, in order to continue protection of valuable plants, subsequent applications of active materials must be made. As the active materials are often poisonous to non-target insects, animals and/or man, repetitive applications usually have undesirable ecological side effects. Excess bio-active material may eventually find its way into drinking water supplies or into food resources, causing cumulative effects on certain birds or animals as overly repetitive applications run off into surrounding soils and into surface or ground water.
To minimize runoff resulting from rainfall it is necessary first of all to use a form of the active material that is substantially water-insoluble. Many protective formulations are applied in a liquid form with the active ingredient emulsified or suspended in an organic solvent-emulsifier with the balance of the formulation made up with water. Where long-term effectiveness is desired and the weather is unfavorable, quick-drying solvents have been used to help ensure the active material is dried onto the foliage before the next rain. If the active ingredient dries to a solid that is substantially insoluble in water, it may form a relatively tenuous mechanical bond to the foliage and exhibit some resistance to mild rainfalls.
Since the active ingredient is usually a very small portion of the applied composition, an insoluble filler with some weather-resistant adhesive characteristics to help bind the active material to the plant foliage is useful. Of course, such a binder material must not be phytotoxic with respect to the plant to be protected. As an example, in Ressler, U.S. Pat. No. 2,098,836, an insecticidal composition is described which includes a polyvinyl alcohol at about 0.2 to 2 percent by weight of an aqueous solution of nicotine. The addition of the polyvinyl alcohol is said to improve the effective life of the insecticide, after it has dried in place, by forming a relatively insoluble film that protects the active-nicotine from loss from the plant foliage through volatilization and the washing action of rain.